A large number of books are published each year in paperback form. These include textbooks and reference books, classics and best sellers, novels and non-fiction works--in short the whole gambit of published books. While many books, notably classics and best sellers, are available in both hard cover and paperback form, a large number of books are published only in paperback form. The latter include not only throwaway novels, but also textbooks and reference books to which the owner refers again and again. A paperback book can be published at much lower cost than that of the same book in hard cover form. For this reason, many books, including textbooks and reference books of limited circulation, are published only in paperback form. On the other hand, paperback books are much less durable than hard cover books. If the owner of a paperback book re-reads it or refers back to it frequently, as he may in the case of a textbook or reference book, the book soon becomes dogeared. The front cover, particularly, becomes worn due to the application of thumb pressure every time the book is opened.
Dust covers which are widely used on hard cover books, offer very little protection to paperbacks. They may protect the covers from stains, but they do nothing to strengthen the covers so that the book can withstand repeated use.
Other printed works, including hardback books, magazines or other periodicals, pamphlets and reprints, are also subject to wear if used frequently. For example, magazines in physicians' offices, and periodicals in technical libraries may be read or referred to frequently by different readers and may become worn or torn in the process. The same may also be true of pamphlets and reprints of articles which are read or referred to frequently. Even hard cover books may lose their freshness if used frequently, because most hard cover books are bound with cloth bindings, which are not stain proof and which become stained from oil and dirt on the fingers of the users after repeated use.
A commercially available laminate for protecting books comprises a pair of identically spaced transparent rectangular sheets, laminated to a thin flexible transparent sheet in spaced apart relationship so that the resulting laminate has stiff portions at either end and a flexible portion in the middle. The middle portion is just slightly wider than the spine of the book to be protected. To apply this laminate to a book, one lays the spine of the book on the middle portion of the laminate, and presses the two stiff sheets, which are adhesive coated, against the covers of the book. Finally, one trims off any excess laminate.
The laminate described above has several disadvantages. First, it must be provided in at least two sizes having middle portions of different widths, to accommodate books of different thickneses (i.e. different spine widths). Second, even with different sizes available, the middle portion of the laminate will usually be slightly wider than the spine width of the book, so that either the edges of the stiff sheets do not coincide with the edges between the covers and the spine of the book, or the flexible portion of the laminate covering the spine is slightly wrinkled. In fact, it is difficult to avoid wrinkles in any case when applying this laminate to a book.